Guns having projectiles propelled by the combustion of liquid propellants are well known. Regenerative liquid propellant feed systems wherein the combustion forces are used to force additional liquid propellant into the combustion chamber are also known. U.S. Pat. No. 2,981,153 to patentees Wilson et al is a typical example of applicable prior art. The regenerative liquid propellant feed system is attractive for very high pressure combustion systems that fire repetitively, such as a gun. Air and/or vapor bubbles in the propellant charge however have posed two serious problems: (1) they are a source of variation in the weight of propellant charged from round to round; and (2) if a monopropellant is used the temperature rise due to adiabatic compression of the bubble may initiate an explosive decomposition behind the piston.
It has been found that bubbles in the charge can substantially be avoided by admitting the propellant in a tangential direction into a cylindrical or annular charge chamber. The swirling of the fuel input to the combustion chamber of jet engines is known as exemplified by U.S. Pat. Nos. 3,355,891 to patentee Rhodes, and 3,426,534 to patentee Murphy. Since this swirling of the fuel is into the combustion chamber and not into a charge chamber, and since these patents are to the jet engine art and not the gun art they are not considered prior art in the field of the invention.